Vitamin D and Restless Legs Syndrome
Restless legs syndrome (RLS) is neurologically related to central iron and dopamine dysfunction. Ferritin is the primary lab to check. Vitamin D deficiency associations exist but are secondary — correct deficiency, but don't skip the ferritin.
Iron first — the ferritin priority
RLS is a "brain iron deficiency" syndrome even at normal peripheral iron. Guidelines recommend checking ferritin and transferrin saturation; treating ferritin below 75 ng/mL with oral iron (ferric maltol or standard ferrous salts) even without frank anaemia. This is the highest-impact intervention for most RLS patients.
Vitamin D evidence
Cross-sectional studies find lower 25(OH)D in RLS patients. Wali 2015 randomised RLS patients to vitamin D or placebo and reported significant IRLS score improvement in the vitamin D group. Small trial. Broader evidence is limited.
Practical approach
- Any adult with RLS: check ferritin, transferrin saturation, CBC, TSH, 25(OH)D, magnesium, B12, glucose.
- Ferritin < 75 ng/mL: iron supplementation (325 mg ferrous sulfate every other day, or ferric maltol).
- 25(OH)D < 30 ng/mL: correct with 2,000 IU/day cholecalciferol.
- Persistent moderate-severe RLS after nutrient repletion: neurology referral; dopamine agonists (pramipexole, ropinirole), alpha-2-delta ligands (gabapentin enacarbil, pregabalin).
- Avoid RLS triggers: caffeine after mid-day, alcohol, sedating antihistamines, some antidepressants.